# Selecting Items In A List With Filters

``````
/* Create an list of items denoting the number of soldiers in each regiment, view the list */
regimentSize = (5345, 6436, 3453, 2352, 5212, 6232, 2124, 3425, 1200, 1000, 1211); regimentSize``````
``````(5345, 6436, 3453, 2352, 5212, 6232, 2124, 3425, 1200, 1000, 1211)
``````

## One-line Method

This line of code does the same thing as the multiline method below, it is just more compact (but also more complicated to understand.

``````
/* Create a list called smallRegiments that filters regimentSize to
find all items that fulfill the lambda function (which looks for all items under 2500). */
smallRegiments = list(filter((lambda x: x < 2500), regimentSize)); smallRegiments``````
``````[2352, 2124, 1200, 1000, 1211]
``````

## Multi-line Method

The ease with interpreting what is happening, I’ve broken down the one-line filter method into multiple steps, one per line of code. This appears below.

``````
/* Create a lambda function that looks for things under 2500 */
lessThan2500Filter = lambda x: x < 2500``````
``````/* Filter regimentSize by the lambda function filter */
filteredRegiments = filter(lessThan2500Filter, regimentSize)``````
``````/* Convert the filter results into a list */
smallRegiments = list(filteredRegiments)``````
``````[2352, 2124, 1200, 1000, 1211]
``````

## For Loop Equivalent

This for loop does the same as both methods above, except it uses a for loop.

### Create a for loop that go through each item of a list and finds items under 2500

``````
/* Create a variable for the results of the loop to be placed */
smallRegiments_2 = []

/* for each item in regimentSize, */
for x in regimentSize:
/* look if the item's value is less than 2500 */
if x < 2500:
/* if true, add that item to smallRegiments_2 */
smallRegiments_2.append(x)``````
``````
/* View the smallRegiment_2 variable */
smallRegiments_2``````
``````[2352, 2124, 1200, 1000, 1211]
``````

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## Two Machine Learning Fields

There are two sides to machine learning:

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